In collegiate football, the focus often shifts from building in the off-season to simply surviving the grind of the competitive schedule. But while an athlete’s total body weight might stay steady during the season what is actually happening to muscle, fat, and bone?

We recently published a study in the Journal of Strength and Conditioning Research (Brooks, SG and Dengel, DR. Position-specific longitudinal assessment of total and regional body composition in NCAA Division I football players. J Strength Cond Res 40(3): e241-e248, 2026) looking at how total and regional body composition change specifically by position over an entire season. In this blog first blog we will look at the changes in lean mass that occurred over the season.

The "mid-season loss in lean mass"
The most striking discovery from tracking 188 Division I players was that while total body mass and fat mass remained relatively stable, total lean mass significantly decreased across the season. This occurred in nearly every position group, including:
Defensive Backs, Offensive Linemen, Punters and Kickers, Running Backs, Tight Ends, and Wide Receivers. Interestingly, Linebackers and Quarterbacks were the only positions that did not show a significant loss in total lean mass, highlighting the need for position-specific monitoring (see figure).

Where is the Muscle Going?
By using Dual X-Ray Absorptiometry (DXA), we were just not looking at totals values for muscle, fat, and bone masses, but we were also looking at regional levels of these masses. What we observed was that the loss in lean mass was not uniform across the body:

Where is the Muscle Going?
By using Dual X-Ray Absorptiometry (DXA), we were just not looking at totals values for muscle, fat, and bone masses, but we were also looking at regional levels of these masses. What we observed was that the loss in lean mass was not uniform across the body:

• The Legs Take the Hit: The majority of lean mass loss occurred in the legs and gynoid (hip and thigh) regions across almost all positions.
• The Trunk Stays Tough: Trunk lean mass remained stable throughout the season for every single position.
• Arm Stability: Arm lean mass generally held steady, with the exception of Defensive Backs, who saw a small decrease.

Why This Matters for Coaches and Training Staff
These findings suggest that the traditional "in-season" approach which often reduces training intensity to prioritize recovery may be inadvertently leading to a loss of the very muscle mass required for peak performance and injury prevention.

The Dexalytics Advantage: Understanding that lean mass loss is concentrated in the lower body allows strength and conditioning staffs to develop targeted interventions. Rather than waiting for a player’s performance to dip, coaches can use regular DXA monitoring to:

• Identify At-Risk Players: Spot early declines in leg lean mass before they impact speed or power.
• Adjust Nutrition: Increase protein or caloric intake specifically for positions showing the highest rates of lean mass loss.
• Tailor Training: Modify in-season lifting programs to emphasize leg and gynoid mass maintenance.

Conclusion

Elite performance is not just about how much an athlete weighs on game day; it's about the quality of that weight. This research confirms that the "in-season slide" is a real phenomenon that affects nearly every position on the field. With the right data, teams can stop the slide and keep their athletes in peak shape all the way to the postseason.

Reference

Brooks, SG and Dengel, DR. Position-specific longitudinal assessment of total and regional body composition in NCAA Division I football players. Journal of Strength and Conditioning Research 40(3): e241-e248, 2026. 

About the Author
Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise, and body composition testing for researchers across the University of Minnesota.